Advances in integrated circuits used in high performance systems have also created a demand for high density electrical interconnects to accommodate large numbers of inputs and outputs. Methods of manufacturing high density substrates are known to those having skill in the art, as described in U.S. Pat. No. 4,810,332 and in Jensen et al., "Copper/Polyimide Materials for High Performance Packaging," IEEE Transactions on Components, Hybrids, and Manufacturing Technology, Vol. CHMT-7 #4, pp. 383-393 (December, 1984).
Fabrication of electronic components such as integrated circuits and high density copper/polyimide substrates invariably includes a certain percentage of defective units, for instance from short-circuited connections or electrical openings. These defects are usually detected during manufacturing by mechanical, optical, or voltage contrast electron beam testing and the like. Or a customized metal layer which is properly constructed may be defective as a result of new routing requirements. Various options may be available to rework these defects. A short-circuit could be severed by a laser beam or an ion beam. An open line could be closed by laser deposition, laser chemical vapor deposition, chemical vapor deposition, or ink jet metal deposition. Nevertheless, it may not be feasible or possible to repair a defect without fabricating the entire layer again. It would be highly advantageous to rework a defective layer on an integrated circuit of a multilevel substrate without damaging the underlying layers so that the remainder of the electronic component can be salvaged.